Atomic processes in near-equilibrium plasmas

Abstract

A rigorous general theory based on non-equilibrium thermodynamics is developed to treat atoms in a steady-state non-equilibrium plasma with strong radiation environment. The atomic radiative properties are described by a linear response matrix, which relates the emission/absorption coefficients to the surrounding radiation environment. The response matrix is calculated by solution of the usual rate equations with special boundary conditions. There is evidence that the range of linear response is large. According to the general theory of non-equilibrium thermodynamics the response matrix must be symmetric and this symmetry gives a powerful test for NLTE codes. In this paper we prove that excited-state populations in a steady-state near-LTE plasma are characterized by the principle of minimum entropy production and derive the exact formula for the response matrix.